This invention relates generally to electronic security and surveillance systems for monitoring a large number of remote installations or facilities by a central monitoring station, and more particularly concerns electronic circuitry and methods for transmitting and receiving security information between each remote installation and the central monitoring station over a transmission medium having a finite information bandwidth.
In general a centrally monitored security and surveillance system includes on-site surveillance equipment installed at a remote facility, a central information monitoring station, and a transmission medium having a limited information bandwidth to interconnect the remote installation and the central station. In such a security system, the on-site surveillance equipment at the remote installation collects information, in electronic form, relating to the security status of the facility being monitored. The information collected by the on-site surveillance equipment is then transmitted via the transmission medium to a central monitoring station where the security information from the on-site surveillance equipment is monitored to determine the security status at the remote installation. When an alarm condition exists at one of the remote installations, the central monitoring station detects that alarm and responds accordingly, such as by calling police or fire fighters.
In prior art central monitored security systems, the on-site surveillance equipment at each remote installation monitors a number of on-site locations. The surveillance equipment often includes microphones, motion detectors, pressure sensors, shock sensors, fire detectors, and the like. The on-site surveillance equipment used in such prior art central monitored security systems collects only a limited amount of security data because the transmission medium can transmit only a limited amount of information to the central station due to its limited transmission capabilities. In some prior art residential central monitored security systems, for example, the security information collected at the remote installation is transmitted to the central monitoring systems, over telephone lines. Such a prior art central monitored security system is limited by the information bandwidth of a typical telephone circuit. Moreover, the expense of a dedicated telephone line results in such systems often relying on a nondedicated line which means that central monitoring of the remote facility is only available during an alarm condition.
Finally, prior art central monitored security systems have not been able to provide video monitoring at the remote facility because of the wide bandwidth required to transmit video information. Without video capability, prior art central monitored security systems cannot confirm whether an alarm signal received at the central station is true or false, and each alarm must be investigated independently by calling either the police or fire fighters.
In order to monitor a large number of remote facilities on a continuous basis and monitor video, audio, and alarm information at the central station, which is often required for large commercial installations, it is necessary to transmit a large amount of security information to the central monitoring station in a secured fashion and to be able to pinpoint the security information that is most important at the central monitoring station. It is also necessary to be able to confirm whether an alarm signal is true or false without sending police or fire fighters to the remote facility.